Fumigants are commonly employed in the sterilization of hydroponic beds, in soil fumigation, and in the fumigation of structures such as warehouses, freight cars, and the like, to kill all living organisms therein.
The fumigant demand for agricultural and horticultural applications is projected to increase 3.7 percent per year to a volume of about 60 million dollars in 1995.
The growth rate of fumigant application has been limited because fumigants such as methyl bromide, chloropicrin and phosphine typically are pesticides in the form of poisonous gases which kill living organisms when absorbed or inhaled. Soil is fumigated to eliminate one or more pests such as insects, worms, bacteria, fungi, weed and grass seeds, and the like.
Methyl bromide, the most widely used fumigant, is a deadly gas which causes nausea and vomiting when inhaled by humans, and in severe cases inhalation can cause coma or death from respiratory failure.
Methyl bromide also is the largest single source of ozone-depleting bromine atoms in the stratosphere. In 1992 the parties to the Montreal Protocol On Substances That Deplete The Ozone Layer amended the treaty to require a freeze by 1995 on production of methyl bromide at 1991 levels. World production of methyl bromide in 1990 was about 63,000 metric tons.
In the United States, where the Clean Air Act requires that ozone-depleting substances be banned completely, the Environmental Protection Agency has set a Jan. 1, 2001 date for phaseout of methyl bromide. Producers and users of methyl bromide are opposing this ban, since there is a lack of readily available substitutes, and the ban will disrupt the growth, shipping and storage of important food crops such as tomatoes, strawberries, and citrus fruits.
There remains a high priority need for gaseous fumigants which can be utilized in agricultural and horticultural applications with relative safety to humans, and which do not have ozone-depleting reactivity.